Constant velocity universal joints used in power transmission devices for automobiles and various industrial machines can be broadly classified into fixed type and plunging type. Plunging constant velocity universal joints allow not only angular displacement but also axial displacement (plunging). However, fixed constant velocity universal joints allow only angular displacement and are used, for example, on the wheel side (outboard side) of the drive shafts of automobiles.
The reduction in size and weight of fixed constant velocity universal joints contributes to an improvement in fuel economy of automobiles and to an increase in flexibility of the layout of the driving systems. Therefore, it is desirable that fixed constant velocity universal joints be reduced in size as much as possible while satisfying the required performance. As shown in FIGS. 2 to 4, a fixed constant velocity universal joint includes, among others, an outer race 10, an inner race 20, balls 30, and a cage 40. To reduce the size and weight of the joint as a whole, Patent Documents 1 and 2, for example, propose that each component is reduced in size and weight. FIG. 3 shows a fixed constant velocity universal joint that is reduced in size and weight as compared with a fixed constant velocity universal joint shown in FIG. 2.
[Patent Document 1] Japanese Patent No. 3460107.
[Patent Document 2] Japanese Patent Application Laid-Open No. Hei 09-317784.